This invention relates to pianos and piano keys.
In the manufacture and maintenance of pianos, piano keys are leveled at a predetermined height with respect to the key bed. The prior art method currently in use for leveling piano keys includes selecting two natural (white) keys (usually the keys at the opposite farthest ends of the keyboard) as guide keys and adjusting these keys with respect to the piano key bed using a gauge or measuring device. The remaining keys on the keyboard are then aligned to the guide keys.
Referring to FIG. 1, in which the prior art key leveling technique is illustrated, paper punchings 104 of varying thicknesses are used to adjust the height of key 100 with respect to key bed 102. The paper punchings are placed between the balance rail 106 of the piano and a bearing 108 upon which key 100 is supported. To access balance rail 106, the action stack (one component 110 of the action stack is shown) and keyboard are removed from the piano, and the action stack is removed from the keyboard. Key 100 and bearing 108 are then removed from balance rail 106, and paper punchings 104 are added or removed. The bearing, key and action stack are then replaced, and the assembly is reinstalled in the piano. The height of key 100 with respect to key bed 102 is then checked. If the height is not correct, the process is repeated until the key is level. Both guide keys are leveled in this manner; then, using a straight edge, laser, sensor or by eyeing, the rest of the keys are adjusted by repeating the steps described above until proper key leveling is achieved for all eighty-eight keys. This process must often be repeated several times, each time allowing time for the wood, felt and paper components of the keyboard to compress and settle. In addition, regular maintenance is required as these parts wear and become further compressed.
This method of key leveling has several drawbacks, including that a seasoned technician requires approximately forty-five minutes to accomplish a single pass at key leveling, which makes the process very time consuming and labor intensive. The repeated removal and replacement of the key sticks can also cause enlargement of the balance rail pin hole in the key stick, resulting in key chucking (back and forward motion of the key) which may in turn cause unstable regulation, inconsistent touch and unwanted noise. The repeated removal and replacement of the action stack may also wear and strip the action hanger screws. Additionally, given the very nature of the method, even a modicum of accuracy is difficult to achieve.